1. Field of the Invention
This invention relates generally to copper and silicon doped aluminum lines used in integrated circuit devices and more particularly to a technique for improving schottky diodes formed between such lines and a silicon body by reducing the formation of parasitic zener diodes in semiconductor devices.
2. Description of the Prior Art
The use of metal interconnecting lines on silicon semiconductor bodies in the formation of integrated circuits is well known. It has been found that if such lines are formed of specific combinations of various metals such as copper, aluminum and silicon, significant benefits and improvements can be realized in the integrated devices formed with such lines. In the prior art it is well known that it is desirable to minimize alloying and penetration of the aluminum in the line into the silicon body during subsequent processing. This is achieved by adding at least 1-2% silicon by weight to the aluminum layer prior to the subsequent processing. By so saturating the aluminum layer with this quantity of silicon, sufficient to satisfy the solubility limits, the rate of alloying and spiking penetration of the aluminum of the line with the underlying silicon body is minimized.
It is also known to the prior art to add approximately 4 to 5 weight % of copper to such aluminum-silicon lines so as to provide a current conductive line which is resistant to circuit failure arising as a consequent of current induced mask transport phenomenon, i.e. electromigration which causes breaking of the lines. This is taught in U.S. Pat. No. 3,725,309 issued Apr. 3, 1973, to I. Ames et al and assigned to the same assignee as the present invention. In addition to using such lines to interconnect the elements forming the integrating circuit such metal lines are also used to form schottky barrier diodes in the integrated circuit. Schottky barrier diodes so formed are determined by the difference in work function between the metal line and the silicon body on which they are formed.
When metal lines comprised of aluminum, copper and silicon are deposited on a silicon body and sintered to form a schottky barrier device adverse effects occur, due to silicon and copper precipitation out of the metal line. Such precipitation can cause the formed schottky barrier diode to fail. This is especially true when both copper and aluminum precipitates coincide, forming a parasitic zener diode.